Why is ECG important?

If you hear a noisy inside your car, you feel uncomfortable, what you will do?Check it out, right? However, when you fell not good about your body, what are you going to do? Take a rest or drink some water and then forget it, right?

People always ignore the message from body and give less care for body than for car. Why? For it is hard to see a Dr. and easy to check car technician.

Mostly, the body will fix by itself finally. That's why we fix car all right but fix body with suffer. Because we always too late to do something for our health.

What can we do for our body like check the car? A lot of the abnormalities seen on an ECG are pointers to health possible problems. It's kind of like that you hear a knock from the front corner of your car. It can't be sure what it actually is until you look closer at the front corner of your car!

An insignificant , potentially dangerous could cause lethal accidence. That's how ECG test function.

Heart diseases are known to afflict millions around the world.

It is estimated that by the end of this decade, heart diseases will be a major killer disease.

Heart diseases are afflicted onto people of all age groups. Prevent is the most important and efficiency key step to free from heart disease and its complication.

Early detection of heart disease can be done with various laboratory tests and analysis, but it was hard for home testing, until now with the Portable ECG monitors, early and rapid detection of any potential life threatening heart rhythm changes can be detected at home.

Some small hand held monitors are capable of detecting a wide range of potentially serious arrhythmias such as tachycardia (including ventricular tachycardia), bradycardia, atrial and ventricular ectopic beats, pauses and atrial fibrillation, as well as ST-segment elevation events.

What is ECG

□An ECG is an Electro-Cardio-Gram, or electrical readout of the heart, this helps physicians see how the heart is beating.

□An ECG is used to measure: Damage to the heart, How fast your heart is beating and whether it is beating normally ,the size and position of your heart chambers.

□An ECG is painless. No electricity is sent through the body. The electrodes may feel cold when first applied.

□To help your heart works as a pump that brings blood to the lungs and the rest of the body, your heart has an electrical system that makes it contracts in an orderly way.

□The electrical impulse that signals your heart to contract begins in the sinoatrial node (also called the sinus node or SA node).

□The signal leaves the SA node and travels through the heart along a set electrical pathway. Different nerve messages signal your heart to beat slower or faster.

The 12 leads ECG measures electrical potential

All cells membranes in the body are charged. In a polarized state (resting) the membrane carries a net + charge. Depolarization: The shift in electrolytes which reverses the charge Repolarization: Return to the resting state

Voltage measurement

Any voltage measurement requires two electrodes: a "reference electrode", whose potential does not change during the cardiac cycle, and an "exploring electrode" attached to the limb in question.

□The ECG trace requires two sensors to measure electric signals from parts of the body on opposite sides of the heart.

□With the bipolar system, one limb is connected to the positive terminal of the recording galvanometer and another limb to its negative terminal. We have the following bipolar leads:

Standard Limb Leads
Lead I : Right Arm (-) to Left Arm (+)
Lead II: Right Arm (-) to Left Leg (+)
Lead III: Left Arm (-) to Left Leg (+)

lead I and Lead II rapid interpretation

Heart rate

□One small square on the ECG is equivalent to 0.04 s; one large square is 0.2 s. The quickest way to calculate the heart rate is to count the number of large squares between QRS complexes and divide into 300, e.g. if there are three large squares, the heart rate is 100 beats/min.

□A heart rate of > 100 bpm is a tachycardia (Fig. 38); < 60 bpm is a bradycardia.

Heart rhythm

Is it regular or irregular?

If there is any doubt, use a piece of paper to map out ten or fifteen consecutive beats and see whether the rate is the same further along the ECG.

Regular rhythms

P wave precedes every QRS complex with consistent PR interval is sinus rhythm.

Arrhythmia

An irregular heartbeat is known as an arrhythmia.

A typical heart rate is 50 to 100 beats per minute.

Arrhythmias and abnormal heart rates don't necessarily happen together.

Arrhythmias can occur with a normal heart rate, or with heart rates that are slow called bradyarrhythmias or less than 60 beats per minute.

Arrhythmias can also take place with rapid heart rates called tachyarrhythmias faster than 100 beats per minute.

Arrhythmias may be caused by several different factors, including:

□Coronary artery disease

□Electrolyte imbalances in

□your blood (such as sodium or potassium)

□Changes in your heart muscle

□Injury from a heart attack

□Healing process after heart surgery

P waves The P waves：

You need to check：

□Are P-waves present?

□Do they occur regularly?

□Is there sinus rhythm (does a P-wave precede each QRS complex?)

□Do the P-waves look normal? (smooth, rounded & upright)

Peaked P wave

□The P wave often has a sharp, peaked appearance.

A、Right Atrial RA enlargement：
P wave amplitude≧ 2.5mm in leads II, III, aVF. The P wave duration<0.12s.

B、Left Atrial enlargement：
P wave duration≧ 0.12s in lead I,II and aVL. Abnormal P-terminal force in V1: the depth and duration≧0.04mm-sec.

□If P waves are present but there is progressive lengthening of the PR interval ending with non-conducted P wave followed by a normally conducted P wave with a shorter PR interval, the patient is in Wenckebach's (or Mobitz type I) 2nd degree AV block.

PR interval

□The PR interval is measured from the beginning of the P wave to the R wave and is usually 1 large square in duration (0.2 s).

□A short PR interval represents rapid conduction across the AV node, usually through an accessory pathway (e.g. Wolff–Parkinson–White syndrome)

QRS wave

□Normal QRS duration is less than three small squares (0.12 s) and represents normal conduction through the AV node and the bundle of His.

A broad QRS complex signifies either:
1. The beat is ventricular in origin, e.g. an ectopic beat, or
2. There is a bundle branch block.
A broad QRS with an 'M' pattern in lead I represents left bundle branch block

T waves

□T waves should be upright in all leads other than leads III and V1 where an inverted T wave can be a normal variant.

□Tall tented T waves could represent hyperkalemia

□T wave inversion can represent coronary ischaemia, previous infarction or electrolyte abnormality such as hypokalaemia.

The ST segment

□The ST segment is the part of the ECG between the end of the S wave & start of the T wave.

□In a healthy individual it should be an isoelectric line (neither elevated or depressed)

□Abnormalities of the ST segment should be investigated to rule out pathology.

ST Elevation

□ST elevation is significant when it is > 1mm (1 small square) in relation to the baseline.

□It is most commonly caused by acute myocardial infarction

□The morphology of the ST elevation differs depending on how long ago the MI occured

ST Depression

□ST depression is significant when it is >1mm (1 small square) in relation to the baseline.

□ST-depression lacks specificity, therefore you shouldn't jump to any diagnostic conclusions.

□It can be caused by many different things including：
Anxiety / Tachycardia / Digoxin toxicity / Haemorrhage / Hypokalaemia / Myocarditis /Coronary artery insufficiency /MI